1. Field of the Invention
The present invention relates to a water discharge device.
2. Description of the Related Art
Improvement of a feeling of cleaning is demanded for a water discharge device for cleaning a human body. The feeling of cleaning is a feeling that depends on a feeling of stimulation caused by water, which is discharged from the water discharge device, hitting the human body and a feeling of massiveness. If the feeling of stimulation and the feeling of massiveness are compared to characteristics of the water, the feeling of stimulation is a physical quantity represented by a flow speed of the water and the feeling of massiveness is a physical quantity represented by an area of the water hitting the human body (also equivalent to a sectional area of the water immediately before hitting the human body). In other words, the feeling of stimulation is the intensity of stimulation of the water felt by a user according to the flow speed of the water. The feeling of stimulation is intensified if the flow speed of the water increases and is weakened if the flow speed of the water decreases. The feeling of massiveness is a volume of the water felt by the user according to the area of the water hitting the human body. The feeling of massiveness is intensified if the area of the water increases and is weakened if the area of water decreases.
On the other hand, improvement of a water saving function is also demanded for the water discharge device. It is necessary to reduce the volume of water discharged from the water discharge device in order to improve the water saving performance. However, the feeling of massiveness is reduced if the volume of the discharged water is simply reduced. It is likely that users dissatisfied with the feeling of cleaning increase.
Therefore, there is proposed a technique for converting continuous linear water discharge into intermittent discharge by a water mass to secure the area of water hitting a human body and not to spoil the feeling of massiveness while consuming a small volume of water. As an example of this technique, a technique described in Japanese Patent Application Laid-Open Publication No. 2001-90151 (Patent Literature 1) is proposed. In the technique described in Patent Literature 1, a first portion where jetting speed is high and a second portion where jetting speed is low are alternately formed in discharged water and the first portion catches up with the second portion before water arrival at the human body to form a large water mass. In the technique described in Patent Literature 1, in order to form such a speed difference, pressure higher than a water supply pressure to the water discharge device is intermittently applied to substantially vary a water discharge pressure. If the water discharge pressure is substantially varied in this way, intermittent flow speed variation occurs in the water discharge. Therefore, the intermittent water discharge by the water mass explained above is realized.
The technique described in Patent Literature 1 is a technique excellent for surely realizing the intermittent water discharge by the water mass. However, a relatively large pump is necessary to apply the pressure higher than the water supply pressure. If the relatively large pump is indispensable, the entire water discharge device becomes expensive, leading to an increase in the size of the device.
As a technique for periodically varying the flow speed of the discharged water without using a pump, a technique described in Japanese Patent No. 4572999 (Patent Literature 2) is proposed. In Patent Literature 2, air bubbles are mixed in discharged water to cause flow speed variation of the discharged water. According to the description of the Patent Literature 2, in a portion where the volume of the air mixed in cleaning water as air bubbles is larger, the speed of the cleaning water is higher. On the other hand, in a portion where the volume of the air mixed in the cleaning water as air bubbles is smaller, the speed of the cleaning water is lower. Consequently, in the discharged water, repetition of the high-speed portion and the low-speed portion occurs.
The technical idea of Patent Literature 2 is an idea for changing the mixed volume of the air in the cleaning water to give flow speed variation to discharged water. However, the examination by the inventors found that it is difficult to give large flow speed variation to discharged water according to the technical idea of Patent Literature 2. Paragraph 0047 of Patent Literature 2 describes that it is desirable to supply fine air bubbles to the cleaning water in order to efficiently mix the air in the cleaning water. However, the inventors found that, even if the fine air bubbles are mixed in the cleaning water and a mixed volume of the air bubbles is changed, it is difficult to give large flow speed variation to discharged water. If the flow speed variation of the discharged water is small in this way, a long time is necessary until a discharged water portion having relatively low speed catches up with a discharged water portion having relatively high speed. Therefore, the water mass sometimes does not sufficiently grow until the discharged water arrives at the target human body.